From 72a2bfcaf01860ce8dd6921490d903dc0ad59c89 Mon Sep 17 00:00:00 2001 From: Abhishek Kumar Date: Sat, 16 Jan 2021 18:11:12 +0000 Subject: [PATCH] commit-graph: add a slab to store topological levels In a later commit we will introduce corrected commit date as the generation number v2. Corrected commit dates will be stored in the new seperate Generation Data chunk. However, to ensure backwards compatibility with "Old" Git we need to continue to write generation number v1 (topological levels) to the commit data chunk. Thus, we need to compute and store both versions of generation numbers to write the commit-graph file. Therefore, let's introduce a commit-slab `topo_level_slab` to store topological levels; corrected commit date will be stored in the member `generation` of struct commit_graph_data. The macros `GENERATION_NUMBER_INFINITY` and `GENERATION_NUMBER_ZERO` mark commits not in the commit-graph file and commits written by a version of Git that did not compute generation numbers respectively. Generation numbers are computed identically for both kinds of commits. A "slab-miss" should return `GENERATION_NUMBER_INFINITY` as the commit is not in the commit-graph file. However, since the slab is zero-initialized, it returns 0 (or rather `GENERATION_NUMBER_ZERO`). Thus, we no longer need to check if the topological level of a commit is `GENERATION_NUMBER_INFINITY`. We will add a pointer to the slab in `struct write_commit_graph_context` and `struct commit_graph` to populate the slab in `fill_commit_graph_info` if the commit has a pre-computed topological level as in case of split commit-graphs. Signed-off-by: Abhishek Kumar Reviewed-by: Taylor Blau Reviewed-by: Derrick Stolee Signed-off-by: Junio C Hamano --- commit-graph.c | 45 ++++++++++++++++++++++++++++++--------------- commit-graph.h | 1 + 2 files changed, 31 insertions(+), 15 deletions(-) diff --git a/commit-graph.c b/commit-graph.c index 123dbc7c21..eb681e6cf5 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -64,6 +64,8 @@ void git_test_write_commit_graph_or_die(void) /* Remember to update object flag allocation in object.h */ #define REACHABLE (1u<<15) +define_commit_slab(topo_level_slab, uint32_t); + /* Keep track of the order in which commits are added to our list. */ define_commit_slab(commit_pos, int); static struct commit_pos commit_pos = COMMIT_SLAB_INIT(1, commit_pos); @@ -772,6 +774,9 @@ static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, item->date = (timestamp_t)((date_high << 32) | date_low); graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2; + + if (g->topo_levels) + *topo_level_slab_at(g->topo_levels, item) = get_be32(commit_data + g->hash_len + 8) >> 2; } static inline void set_commit_tree(struct commit *c, struct tree *t) @@ -960,6 +965,7 @@ struct write_commit_graph_context { changed_paths:1, order_by_pack:1; + struct topo_level_slab *topo_levels; const struct commit_graph_opts *opts; size_t total_bloom_filter_data_size; const struct bloom_filter_settings *bloom_settings; @@ -1106,7 +1112,7 @@ static int write_graph_chunk_data(struct hashfile *f, else packedDate[0] = 0; - packedDate[0] |= htonl(commit_graph_data_at(*list)->generation << 2); + packedDate[0] |= htonl(*topo_level_slab_at(ctx->topo_levels, *list) << 2); packedDate[1] = htonl((*list)->date); hashwrite(f, packedDate, 8); @@ -1336,11 +1342,10 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx) _("Computing commit graph generation numbers"), ctx->commits.nr); for (i = 0; i < ctx->commits.nr; i++) { - uint32_t generation = commit_graph_data_at(ctx->commits.list[i])->generation; + uint32_t level = *topo_level_slab_at(ctx->topo_levels, ctx->commits.list[i]); display_progress(ctx->progress, i + 1); - if (generation != GENERATION_NUMBER_INFINITY && - generation != GENERATION_NUMBER_ZERO) + if (level != GENERATION_NUMBER_ZERO) continue; commit_list_insert(ctx->commits.list[i], &list); @@ -1348,29 +1353,26 @@ static void compute_generation_numbers(struct write_commit_graph_context *ctx) struct commit *current = list->item; struct commit_list *parent; int all_parents_computed = 1; - uint32_t max_generation = 0; + uint32_t max_level = 0; for (parent = current->parents; parent; parent = parent->next) { - generation = commit_graph_data_at(parent->item)->generation; + level = *topo_level_slab_at(ctx->topo_levels, parent->item); - if (generation == GENERATION_NUMBER_INFINITY || - generation == GENERATION_NUMBER_ZERO) { + if (level == GENERATION_NUMBER_ZERO) { all_parents_computed = 0; commit_list_insert(parent->item, &list); break; - } else if (generation > max_generation) { - max_generation = generation; + } else if (level > max_level) { + max_level = level; } } if (all_parents_computed) { - struct commit_graph_data *data = commit_graph_data_at(current); - - data->generation = max_generation + 1; pop_commit(&list); - if (data->generation > GENERATION_NUMBER_MAX) - data->generation = GENERATION_NUMBER_MAX; + if (max_level > GENERATION_NUMBER_MAX - 1) + max_level = GENERATION_NUMBER_MAX - 1; + *topo_level_slab_at(ctx->topo_levels, current) = max_level + 1; } } } @@ -2106,6 +2108,7 @@ int write_commit_graph(struct object_directory *odb, int res = 0; int replace = 0; struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS; + struct topo_level_slab topo_levels; prepare_repo_settings(the_repository); if (!the_repository->settings.core_commit_graph) { @@ -2132,6 +2135,18 @@ int write_commit_graph(struct object_directory *odb, bloom_settings.max_changed_paths); ctx->bloom_settings = &bloom_settings; + init_topo_level_slab(&topo_levels); + ctx->topo_levels = &topo_levels; + + if (ctx->r->objects->commit_graph) { + struct commit_graph *g = ctx->r->objects->commit_graph; + + while (g) { + g->topo_levels = &topo_levels; + g = g->base_graph; + } + } + if (flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS) ctx->changed_paths = 1; if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) { diff --git a/commit-graph.h b/commit-graph.h index f8e92500c6..00f00745b7 100644 --- a/commit-graph.h +++ b/commit-graph.h @@ -73,6 +73,7 @@ struct commit_graph { const unsigned char *chunk_bloom_indexes; const unsigned char *chunk_bloom_data; + struct topo_level_slab *topo_levels; struct bloom_filter_settings *bloom_filter_settings; };